HP 42s resurrection—so simple!


My 42s had two keys die recently—the number 2 key and the exit key. I had to remove the batteries and short out the terminals to get it going, but the two dead keys still didn’t work. I also lost all the data I’d programmed in when I shorted out the terminals.

After numerous attempts to revive my old faithful of fifteen years, I sent an email to fixthatcalc to see if it could be repaired. They replied that it couldn’t be fixed because of the keys not operating.

I bought the latest HP50G calculator to replace it, but was not impressed with the extra keystrokes I had to do for simple operations, compared to the 42s. I really wanted my old 42s back, so bought a HP17Bll (pioneer body) on ebay, to swap the keypad mechanisms over.

While waiting for the 17Bll to arrive, I bought a spray can of solvent based cleaner/lubricant for switches, and sprayed in the gap around the faulty keys of the 42s, and voila!! it started up straight away, passed the self test and is still operating nicely today. If I had have known this, I wouldn’t have shorted out the terminals and lost all my data.

Hopefully some of you who have faulty 42s calcs can revive them by this method—I’m still grinning, and quite happy to spray some more lubricant in if it stops again.

john dagis Australia


I used isopropanol alcohol (probably similar to your switch cleaner) on an unreliable ON key on a 41C a little wiggling of the button and it worked.

I suspect this wouldnt work for keyboards with a plastic sheet under the keys though.

Well done! :)

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